An electronic device such as a mobile phone includes a casing including an upper casing and a lower casing made of a synthetic resin, a plurality of component built-in modules that each have a plurality of electronic components mounted thereon and that are housed in the casing, a display and a battery.
On the other hand, in recent years, demand has been increasing for smaller and thinner electronic devices to greet the full-fledged arrival of a ubiquitous network society. In a structure that houses constituent components such as component built-in modules, a display, a battery and the like within a casing that is prepared in advance such as a mobile phone, the realization of further reductions in thickness is becoming difficult.
In contrast to this, Patent Document 1 discloses a constitution in which a component built-in module including an electronic component mounted on a wiring substrate is built into at least a part of the resin casing that includes an upper casing and a lower casing and sealed. In this Patent Document 1, by having at least one of the plurality of component built-in modules built into the resin casing, it is possible to cut down the space within the casing, and thereby enable a further reduction in thickness.
Patent Document 2 discloses a means of reducing the thinness of a printed wiring board on which are mounted electronic components of differing heights. As this means, Patent Document 2 discloses a structure (component built-in module) in which protrusions and recessions or curved surfaces are provided on a printed wiring board so that the heights of the plurality of electronic components mounted on the printed wiring board are the same on both surfaces.
Patent Document 3 discloses an in-molded item incorporating an electronic component (component built-in module) that is formed by in-mold integral molding an electronic component in a long fiber reinforced resin layer. Also, in this Patent Document 3, by making the coefficient of linear expansion of the inner layer part in the long fiber reinforced resin layer less than the coefficient of linear expansion of the surface layer part, a surface with few irregularities and with excellent planar smoothness is formed.
Patent Document 4 discloses a structure that houses an electronic component in an electronic component housing recess that is provided in a flexible substrate, and fills a sealing resin in this recess.